Currently as a radio access technology (RAT) which is a radio access technology, wideband-code division multiple access (W-CDMA, non-patent document. 1) regulated by 3rd Generation Partnership Project (3GPP) has been standardized as the third-generation cellular mobile communication method and service utilizing it has been started.
Moreover, evolved universal terrestrial radio access (evolution of third-generation RAT, hereinafter referred to as EUTRA) and evolved universal terrestrial radio access network (evolution of third-generation access network, hereinafter referred to as EUTRAN) have been discussed. For EUTRA, orthogonal frequency division multiplexing access (OFDMA) has been proposed as a communication method (non-patent document 2).
The EUTRA, which is a standard of the next-generation communication, uses the third-generation (3G) technology as its basis and employs OFDM or the like to enhance larger capacity and higher speed in mobile communication. Although it is assumed that the 3G technology is basically adhered, on the other hand, there are many problems that must be but cannot be solved by the 3G technology.
An uplink random access channel (RACH) sequence in an uplink in EUTRA is an important procedure for a mobile station and a base station in carrying out connection processing there between (e.g., importance thereof is pointed in non-patent document 3). However, procedure or meaning thereof differs greatly in the 3G technology and EUTRA standard.
That is, according to the 3G technology, a random access channel (RACH: a channel which enables a mobile station to transmit to a base station at an arbitrary timing and is used for establishing an uplink) is not orthogonal to a data channel and therefore there may be a case where interference occurs between the RACH and the data channel. Therefore, what is called power ramping is required so that transmission power is gradually increased on the mobile station side until the base station can receive data (e.g., refer to pp 45-47 “2-2-3 Random access” in the above-mentioned non-patent document 1).
Here, random access in uplink by the W-CDMA method will be briefly explained using FIG. 22. FIG. 22 is a flowchart showing procedures of random access in uplink by the W-CDMA method.
A mobile station which carries out initial transmission, that is, a mobile station right after power thereof is turned on or a mobile station intermittently receiving data, is required to transmit a random access channel (RACH) to a base station first to establish an uplink between the base station. Because the RACH is used before respective uplink resource is allocated, there is a case where transmission frequency and timing of the RACH are the same as those of another mobile station. At this time, due to degraded transmission signal caused by interference between stations, the base station cannot correctly receive the RACH.
Therefore, as shown in FIG. 22, the mobile station randomly selects a data signal row specifying a transmission mobile station called RACH Preamble first and transmits it to the base station (Step S20). If Acknowledge (ACK) indicating a transmission permit is returned from the base station for the RACH Preamble (Step S21), actual data transmission called RACH message is started (Step S22). On the other hand, in a case where ACK is not returned from the base station (Step S21), or Not Acknowledge (NACK) is returned, transmission power of the RACH Preamble is increased (Step S25) and transmission of the RACH Preamble is carried out again. While confirming whether predetermined number of retransmission has been finished (Step S23), same processing is repeated. If ACK from the base station cannot be received even after the predetermined number of transmission has been finished, it is judged that RACH transmission failed (Step S24) and the procedures are finished.
On the other hand, in a mobile communication method using OFDM (method of EUTRA), because RACH is orthogonal to a data channel, there does not basically occur an interference between the both sides and therefore power ramping as described above is not required.
Instead, however, in the OFDM communication, transmission timing correction on the mobile station taking influence of multi-path into consideration (processing for establishment of temporal synchronization on the basis of transmission timing correction information from the base station) and allocation processing of a communication resource by scheduling on the base station are required. These processings are processings unique to a case of utilizing the OFDM and 3G technology cannot be incorporated. Therefore, a new connection processing technology between a mobile station and a base station is requested.    Non-patent document 1: Tachikawa, K, 2001. “W-CDMA Mobile Communication Method”: Maruzen Co., Ltd.    Non-patent document 2: 3GPP TR (Technical Report) 25. 814, V1. 4. 1 (2006-5), Physical Layer Aspects for Evolved UTRA. http://www.3gpp.org/ftp/Specs/html-info/25814.htm    Non-patent document 3: Ericsson. “E-UTRA Random Access”, 3GPP TSG RAN WG1 Meeting #43, Seoul, Korea, 7-11 Nov. 2005